She's one of the prewar ones, not one of the warbuilts you mention. The bridge profiles are different (flatter front on the later ones)
ROCHESTER CASTLE of 1937 and ROSLIN CASTLEof 1935 are the only one that I know of that had survived until the 60s.
Looks OK to me. I think Rochester over Roslin due to differences in bridge, but hard to be 100% certain at that resolution. Roslin had less plating on the bridge side and I can't find any pics of her with bridge wing cabs which this vessel appears to have. Rochester seems to have had these latterly. (I'm going on pics on photoship)
Hello Alan - a very good panorama of the 'Tilbury side' with from left to right..
Port of London Health Authority hospital 'Hygeia' - 'World's End' pub Tilbury.
Rochester Castle with possibly Watkin's tug Hibernia alongside.
Over No 4 of Rochester Castle is Tilbury Fort and just behind her is the
Hailing Station from which colliers received their orders through a loud hailer.
Then a 'Cock' tug.
Most of that shore line is now out of sight behind the flood barrier..
I think you are a very brave man even to say for certain this is one of the prewar ones. Don't get me wrong - I think you are correct because of the single big vent aft which as far as I can tell none of the wartime/postwar ones had. But if you pointed a gun to my head I'd be reluctant to eliminate anything but Riebeeck & Rustenburg. As for distinguishing between Roslin & Rochester? Sooner you than me with a profile view and at this distance with a blurry photo.
Downloading the photo, zooming in, reducing contrast and brightness makes the greater step size of the front of the bridge pretty clear. Seperating Rochester from Roslin is a bit more tricky. Looking through the variety of photos of both on photoship.co.uk, I can find several photos of Rochester with bridge wing cabs (which the vessel appears to have) though none of Roslin. Also the plating at the side of Rochester goes back further on Rochester than Roslin. (I'm not sure what the correct term for this might be), though with the rather overexposed highlights its hard to 100% certain. I was interested to see if other posters had alternative views.